In recent years, as communication systems have advanced remarkably, they have been exposed to a diversity of cyber attacks. As a result, countermeasure against cyber attack has been sought.
Likewise, mobile terminals are exposed to cyber attacks and the mobility of the mobile terminal causes itself to be exposed to complicated cyber attacks.
In particular, if an SIM (Subscriber Identification Module) is illegally obtained from a mobile terminal that has not been SIM-locked, it is likely that cyber attack will be conducted through the SIM.
In 3GPP (Third Generation Partnership Project), an LTE (Long Term Evolution) system, which is a new communication system, has been standardized (refer to Patent Literature 1 and so forth).
However, in the standard protocol defined in 3GPP, a core-network side PDN-GW (Packet Data Network-Gateway) in the LTE system is provided with a DPI (Deep Packet Inspection) function that detects illegal traffic.
In other words, according to the standard protocol defined in 3GPP, an eNB (evolved Node B) of the LTE system cannot directly monitor the contents of user data. Thus, illegal traffic has to be detected using the DPI function of the core-network side.